Technical Field
Embodiments of the subject matter disclosed herein relate to an exhaust gas recirculation (EGR) system, a cooler for that system, and associated methods.
Discussion of Art
Engines may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system, a process referred to as exhaust gas recirculation (EGR). In some examples, a group of one or more cylinders may have an exhaust manifold that is coupled to an intake passage of the engine such that the group of cylinders is dedicated, at least under some conditions, to generating exhaust gas for EGR. Such cylinders may be referred to as “donor cylinders.” In other systems, the exhaust gas may be pulled from a manifold.
Some EGR systems may include an EGR cooler to reduce a temperature of the recirculated exhaust gas before it enters the intake passage. The exhaust gas recirculation (EGR) cooler may be used to reduce exhaust gas temperature from about 1000 degrees Fahrenheit to about 200 degrees Fahrenheit. Some EGR coolers may fail during use due to high stress concentration in cooling tubes at a connection point between the cooling tubes and a tube sheet of the EGR cooler. Compressive forces may act on the cooling tubes due to constraints on ends of the cooling tubes by a sidewall of a housing of the EGR cooler, thereby resulting in degradation of the tube-tube sheet joint. Stress concentrations on the tubes may be greatest at a leading edge of the EGR cooler, the edge that is closest to an exhaust inlet of the EGR cooler, due to increased thermal gradients at this location.